The invention concerns a tool and a device for crimping contacts onto flexible circuits as well as a crimping station particularly designed for the assembly and creation of bundles provided with connectors on flexible circuits.
Flexible circuits are electrical circuits having an insulating sheet on which conductive tracks are positioned, these tracks being themselves possibly covered with a second protective insulating sheet.
Such circuits are notably coupled to electrical contacts by a technique of piercing the insulation and crimping, and the use of contacts provided with a crimping end having points arranged in a crown and orientated perpendicularly to the flexible circuit to be coupled is known for this purpose. Document U.S. Pat. No. 4,749,368 notably describes the creation of contact elements and coupling of components provided with connection points arranged in a crown.
Contacts are crimped onto the flexible circuit traditionally by positioning the contacts under the flexible circuit facing the conductive tracks of the flexible circuit and then by crimping the contacts onto the flexible circuit by means of crimping matrices formed at the end of cylindrical pins mounted in a framework, a pressing device coming to apply the cylindrical pins onto the flexible circuit of the side facing the crowns, at the center of the crowns, a surface forming an anvil being positioned under the contacts in order to apply a counter-pressure. The result of the crimping operation is a piercing of the insulation by the points, the points being then bent back into petals.
The principle for using such pins, for example, is described in the document xe2x80x9cSAE technical paper series 870553 Flex foil crimp technologyxe2x80x94International Congress and Exposition, Detroit, Michigan, Feb. 23-27, 1987.
The diameter of the crowns is of the order of a few millimeters for the circuits and for the contacts designed to conduct currents of the order of several amperes.
For flexible circuits with a large number of tracks with, for example, an interval between the tracks of 1 to 5 mm, it is necessary to precisely mount a large number of pins in a framework that is in turn provided with holes for taking up the pins machined with a great precision, the pins having, moreover, at the level of their crimping ends, a very strict coplanarity.
Such an embodiment is costly and, even if the pins have a long service life of the order of 800,000 crimpings, risks of breakage exist and the operation of replacing a pin is complex, each of the pins being held in the framework by shafts mounted perpendicularly to the pins in the framework.
Moreover, during crimping, the pins may come into contact along an axis different from the perpendicular axis passing through the center of the crown. In this case, the crimping imprint will have irregularities in the shape of the petals and, in a particularly unfavorable case, a point may not be bent back or may remain imprisoned in the insulation, thus leading to a degradation of the electrical and mechanical crimping characteristics.
The present invention notably proposes a simplified and non-cumbersome structure of crimping matrices which permits very precisely controlling the intervals between the crimping matrices and the coplanarity of the matrices and minimizing the defects obtained during crimping by conducting a controlled simultaneous bonding of all the points.
For this object and according to a first subject, the invention is principally based on the creation of a tool for crimping electrical contact paddles onto conductive tracks of a flexible circuit, this tool having a multipoint network of crimping matrices made up of a solid block having at least one flat surface on which a network of paving blocks of polygonal section and flared base is machined, the xe2x80x9cpaving blocksxe2x80x9d making up the matrices.
The paving blocks notably have a profile that forms a curve on each of their lateral faces a curve widening from the terminal section of the paving block toward the base of the paving block, the coupling zone between the paving block and the block.
In an advantageous manner, the block making up the multipoint matrix can have a network of paving blocks over each of two surfaces.
In a particular mode of embodiment designed for contacts provided with crimping points arranged in a crown, the terminal polygonal section of the paving blocks is oriented so that the lateral faces of the paving blocks come into contact with the crimping points during the crimping operation so as to press back the points and make them into petals.
The invention also concerns a device for simultaneous crimping onto a flexible circuit of electrical contact elements aligned in a plane.
This device is designed for the crimping of a connector provided with a plurality of contacts. In this type of connector, the contacts have, on one side, an end part for coupling to a flexible circuit, this end part having a paddle provided with points arranged in a crown, the points being made by a cross punching of the paddle and then stamping the paddle to fold back the points and open up a circular hole, forming the crown.
On the other side, the contacts have an end part for connection with a complementary contact, the contacts and the flexible circuit being taken up in an insulated housing provided with an open zone releasing the crimping zone of the contacts onto the flexible circuit above and below the crimping zone.
In order to crimp the contacts, on one side, the device has an anvil forming a lower support surface for the electrical contact elements, and on the other side, the crimping device has a mobile pressing device provided with a block whose surface parallel to the alignment plane of the contacts has a plurality of crimping matrices made up of paving blocks with a terminal polygonal section.
The anvil positioned under the paddles can have at least one positioning element and advantageously two positioning elements facing the crowns of two contacts positioned at each end of the flexible circuit, each positioning element being introduced into one of the circular holes of the crowns.
The flexible circuit is then positioned on the paddles and the block is applied by the press onto the flexible circuit, each of the matrices locally and strongly applying the flexible circuit onto the points so as to pierce the flexible circuit and then to bend the points which thus come to crimp the paddles onto the flexible circuit and to effect the electrical connection between the contacts and the tracks of the flexible circuit.
The anvil and press assembly provided with a crimping block according to the invention thus constitutes an optimized crimping device permitting a precision crimping with great reproducibility of the crimpings and making a crimping imprint which can inspected by a camera device with a minimized error rate.
The paving blocks constituting the crimping matrices will be implanted as a function of the number of contacts per connector and the number and arrangement of the crimping crowns. A device for which the paving blocks will have a different polygonal section as a function of the diameter of the crowns is, of course, possible.